WASHINGTON - The Trump administration is working on an expanded U.S. missile defense policy that would address certain threats from Russia and China, departing from a previous strategy that focused nearly exclusively on rogue nations such as North Korea and Iran.

The new policy will still call for bolstered technology against rogue states, with a particular focus on weapons to intercept North Korean leader Kim Jong Un's missiles. But people familiar with the review say it will also mention the need to consider missile threats from Russia and China, a change from previous doctrine.

The document remains in a draft form and could change before its tentative release in late March.

Deliberations on the policy at the Pentagon come as Russian President Vladimir Putin threatens the United States with new weaponry, including a nuclear-powered cruise missile that he touted publicly for the first time during a presidential address on Thursday.

Russia's thousands of missiles easily could overwhelm existing U.S. missile defenses in the event of a full-scale war. Washington relies on the threat of its own vast nuclear arsenal to deter an attack from a global power.

As a result, the Pentagon isn't pursuing a shield against all missile threats from Russia and China. American defense planners abandoned such lofty goals after the Soviet Union's collapse. Rather, according to one U.S. official, the policy will more discretely look at ways the United States can better deal with burgeoning missile threats from Russia and China in regional theaters such as Europe and Asia, where the two countries' systems have alarmed the American military.

The Pentagon so far sees "anything in the regional context as fair game," said the official, who like others spoke on the condition of anonymity because the policy hasn't been finalized. American generals have been calling for better sensors, for example, to track cruise missile threats.

U.S. officials recognize that the advanced missile technologies Russia and China are developing will probably end up in the arsenals of other countries in the future, meaning the policy must decide how to address them anyway.

The Pentagon's chief spokeswoman, Dana W. White, emphasized in a briefing Thursday that U.S. missile defenses aren't trained on Russia and remain focused on rogue nations. The American military already knew about the weapons Putin referenced and stands ready to defend the United States, she said.

White didn't say whether Russian and Chinese threats would be mentioned in the new policy.

The move to adjust the doctrine comes as the Trump administration reworks foreign and defense policies to fit a new national security strategy that has proclaimed the return of "great power competition" with Russia and China.

Critics warn that these systems encourage competitors to develop more sophisticated arms, are expensive and have questionable effectiveness.

"Putin's announcement is a predictable reaction to the ongoing missile defense efforts of the United States," Lisbeth Gronlund, senior scientist at the Union of Concerned Scientists, said in a statement. "Now, it appears that the Trump administration is going to ramp up these defenses, increasing Russia's concerns."

But administration officials and top lawmakers have said the United States must respond to the threats at hand, regardless of whether certain initiatives would rankle Moscow or Beijing.

"It is foolish to try and pick and choose what aggression we will stand against and which we will let go unanswered," House Armed Services Committee Chairman Mac Thornberry, R-Texas, said in a statement. "It is not enough to advocate for a more robust cyber response to Russia's attempts to meddle in our elections but waiver on our response to their renewed nuclear and territorial ambitions."

Faster, more nimble missiles

The concept of U.S. missile defense emerged in the early days of the Cold War with the goal of protecting the American homeland from the Soviet Union's growing arsenal.

The idea rose to new heights in the 1980s with President Ronald Reagan's Strategic Defense Initiative, or Star Wars, which envisioned a shield guarding the United States from Soviet nuclear missiles like "a roof protects a family from rain." Among the main ideas: downing enemy missiles from space.

The initiative, which drew controversy for its high costs and futuristic ambitions, ended after the Soviet Union's collapse, and U.S. missile defense soon reoriented toward a narrower goal of preventing a nuclear missile attack by a rogue nation, or downing a missile accidentally fired by Russia.

In 2002, the United States abrogated the Anti-Ballistic Missile Treaty with Russia, citing the need for a missile defense system that could prevent the United States from being blackmailed by a nuclear-armed rogue nation.

The U.S. military currently has 44 interceptors in Alaska and California that can shoot missiles out of silos, with plans to increase the number to 64 by about 2023 and possibly add a third site in the eastern part of the United States. The military and its allies also operate sea and land missile defense systems in Europe and Asia.

The system in Alaska and California has drawn criticism for its high cost and questionable record; only 10 of the system's 18 intercept tests since 1999 have hit their targets. Proponents point out that the two most recent tests succeeded, including one last year, and say the system has improved.

The Trump administration delayed publication of an initial draft of the new policy, according to U.S. officials, and began reworking it out of concern that it focused too squarely on North Korea and Iran.

The Pentagon long called the document the Ballistic Missile Defense Review, or BMDR, but officials have dropped the "B" because the policy will probably touch on threats from cruise and hypersonic missiles, technologies that Russia and China have been advancing.

Russia has developed new cruise missiles that are capable of hitting targets "at ranges we haven't seen before," the commander of U.S. Northern Command, Air Force Gen. Lori Robinson, said in Senate testimony last month. She urged lawmakers to step up efforts to counter them.

Air Force Gen. John Hyten, the commander of U.S. Strategic Command, warned that Russia is continuing to violate the Intermediate-range Nuclear Forces Treaty, or INF Treaty, with banned ground-launched cruise missiles. Russia also is modernizing heavy bombers to launch other advanced cruise missiles, including those it has put on display in Syria, he said.

Hyten called China's ballistic missile development program the world's "most active and diverse."

China has added road-mobile intercontinental ballistic missiles to its arsenal and improved its sea-launch ballistic missiles, while advancing rapidly toward hypersonic capabilities - or missiles that can evade defenses by traveling many times the speed of sound.

"China's impressive military buildup could soon challenge the United States across almost every domain," U.S. Pacific Commander Adm. Harry Harris said in recent congressional testimony.

Current U.S. missile defenses focus on downing ballistic missiles that fly slower and at an arc. The United States possesses limited ability to counter cruise missiles, let alone hypersonic ones. Cruise missiles fly fast and low and maneuver like planes, evading radars the United States uses to detect missile threats.

U.S. generals are advocating extensive investments in sensor technology. The first step toward better defenses, they say, would be to know in advance when the faster, more nimble missiles are coming.

Above all, the new missile defense policy is likely to focus heavily on ways to defend the United States against North Korea that go beyond the silo-based interceptors the U.S. military currently operates.

One possibility is what's known as "left of launch" or "missile defeat" - military parlance for destroying a missile before it takes off.

To successfully attack a mobile missile before launch, though, the U.S. military would need sufficient intelligence and sensors to track the target and convey its location, in addition to weapons that could eliminate the missile quickly.

The Pentagon will also elaborate on possible ways to intercept North Korean missiles in their "boost phase," or during their ascent. The primary options include shooting them with interceptors fastened to drones or fighter jets, zapping them with solid-state lasers or striking them from weapons in space. Each option comes with technological challenges the Pentagon has yet to solve.

A number of lawmakers have been pressing the Pentagon to deploy ground-based interceptors at a new East Coast missile site - which theoretically would allow the military to take a second shot at a missile coming from North Korea and a first shot at a missile from Iran.

The military has placed three bases in New York, Ohio and Michigan on the shortlist to house the theoretical East Coast site. Congress has asked the Pentagon to select among the three within 60 days of releasing the new policy.